Generally, a ‘robot cleaner’ refers to an apparatus that automatically moves in a predetermined range of working area without requiring manipulation of an operator, performing assigned jobs such as a cleaning job that draws in dust or foreign substances from the floor, or a security job that checks on the doors, windows or gas valves at home.
The robot cleaner determines, through a sensor, the distance to an obstacle at home or office, for example, the distance to the furniture, office equipment, wall, etc., and performs assigned jobs while running in the path on which it would not collide with the obstacles based on the information as detected.
Generally, the robot cleaner is provided with a battery that supplies necessary power for driving, and a rechargeable battery is usually used for this purpose. The robot cleaner is formed with an external recharging apparatus as one system so that the battery can be recharged as necessary.
In order to return the robot cleaner to the external recharging apparatus for recharging, the robot cleaner is required to know where the external recharging apparatus is located.
Conventionally, for determination of where the external recharging apparatus is located, the external recharging apparatus sends out a high frequency signal, and the robot cleaner receives the high frequency signal from the external recharging apparatus and thus finds the location of the external recharging apparatus according to the level of the received high frequency signal.
However, according to the above method that finds the location of the external recharging apparatus based on the level of the detected high frequency signal, determination of the location of the external recharging apparatus is sometimes inaccurate when the level of the high frequency signal varies by the external factors such as reflective waves, interferences, or the like.
Even after the exact location of the external recharging apparatus is found, the power terminal of the external recharging apparatus and the recharging terminal of the robot cleaner may be improperly connected.
In an attempt to overcome the above problems of the prior art, the Applicant has disclosed, “Robot Cleaner System Having External Recharging Apparatus and Docking Method for Docking the Robot Cleaner with External Recharging Apparatus” in U.S. Pat. No. 6,748,297, filed Oct. 31, 2002, which enables the robot cleaner to determine the exact location of the external recharging apparatus and dock with the external recharging apparatus.
According to U.S Pat. No. 6,748,297, the robot cleaner determines the location of the external recharging apparatus using an upper camera and a location recognition mark on a ceiling. Docking with the external recharging apparatus is always accurately made because the process is controlled using a signal from a bumper and a contact signal between the recharging terminal and the power terminal.
However, the robot cleaner system of U.S. Pat. No. 6,748,297 has a limitation in the installation space of the external recharging apparatus. That is, the external recharging apparatus is only formed within the area that is recognizable by the upper camera of the robot cleaner. Accordingly, in the area which is larger than the detectable range by the upper camera, the robot cleaner system can not be efficiently used.
Therefore, a need for a robot cleaner system and a docking method thereof, which enables the robot cleaner to detect the location of the external recharging apparatus even in the outside of the recognizable range of the upper camera, and accurately dock with the external recharging apparatus, has been noted.